A semiconductor power element used in an inverter circuit for driving an automobile motor is available as a power element package integrated with a mold resin, where a power element is sandwiched between heat sink plates of radiating members (refer to JP-A-2001-156225 or USP-2003/0132530 A1). The power element includes an IGBT (Insulated Gate Bipolar Transistor) as a typical power element. The power element of the IGBT is sandwiched between the heat sink plates while an emitter or collector of the power element is connected using solder with the heat sink plate directly or via a spacer. Here, the heat sink plate functions as a path of a large electric current. A gate (control electrode) of the power element is electrically connected with a lead terminal for control signals that is outwardly protruding from the mold resin via a bonding wire. The power element is thus constructed as a power element package. A plurality of the power element packages is assembled to constitute a module of inverter circuit.
In addition, increase of the dimensions of the heat sink plate is proposed to further reduce thermal resistance of the power element package. This proposal involves problem in connection structure where a power element is connected using the boding wire, as explained above, with a lead terminal for control signals to the power element. Here, to maintain connection reliability a wire length is required to be at most 10 mm. The wire length of more than 10 mm potentially involves, during the resin molding, mutual contact between the adjoining wires or breakage of the wire. The connection structure using the bonding wire is therefore improper for increasing the dimensions of the heat sink.